1. Field of the Invention
The present invention relates to a satellite, a mobile terminal, and a complementary terrestrial component in an orthogonal frequency division multiplexing (OFDM) based multi-beam satellite system reusing the same frequency band for all the beams, and a communication method thereof.
2. Description of the Related Art
A mobile satellite communication apparatus may provide telecommunication services in urban areas and the suburbs via a terrestrial/satellite convergence network, using a complementary terrestrial component such as a repeater, a complementary ground component, an ancillary terrestrial component, and the like. In this instance, the mobile satellite communication apparatus may provide telecommunication services via a satellite in the countryside or the suburbs where a line of sight (LOS) is secured. In the urban areas or indoor environments where a satellite signal is not secured, the mobile satellite communicate apparatus may provide telecommunication services using the complementary terrestrial component.
Like a terrestrial cellular mobile communication system based on a base station, a mobile satellite communication system using a multi-beam satellite may divide a service area into a plurality of cells using multiple beams. A mobile terminal may receive a service via a frequency corresponding to a beam where the mobile terminal is located.
FIG. 1 illustrates a beam plan that is used in an existing mobile satellite communication apparatus and of which a frequency reuse rate is 1/7.
Referring to FIG. 1, as a mobile satellite communication system provides a communication service using a difference frequency for each beam, seven frequencies may be required to provide the communication service in seven beams, respectively. Here, the mobile satellite communication system may use all the orthogonal frequency division multiplexing (OFDM) subcarriers for each frequency in each beam. However, in the mobile satellite communication system, every time the mobile terminal moves from a beam to another beam, a frequency is changed and thus a handover time may increase. Also, as a broadband service is provided, a use frequency may increase.
In order to outperform the above disadvantages, as shown in FIG. 2, the mobile satellite communication system may provide the communication service using a beam plan of which a frequency reuse rate is 1/3. As described above, every time the mobile terminal moves between beams, the frequency is changed and thus the handover time may increase. Also, as the broadband service is provided, the use frequency may increase.
Accordingly, there is a need for a mobile satellite communication apparatus and method that may increase a frequency reuse rate and thereby may enhance spectral efficiency.